The present invention relates to fluidized bed combustion and in particular to apparatus for supporting a tubular heat exchanger immersed in a fluidized bed.
In present fluidized bed combustion systems, the feed solids are typically discharged through nozzles or openings located in or above the fluidized bed. Combustion air serves as fluidizing air and is supplied to an air plenum located beneath the fluidized bed. The fluidizing air passes upwardly from the air plenum into the fluidized bed through a perforated bed support plate at a flow rate sufficiently high to fluidize the feed solids within the fluidized bed. The feed solids are comprised of sulfur oxide sorbent and sulfur containing carbonaceous fuel. Combustion occurs in the fluidized bed and in the freeboard region above a bed. The combustion flue gases exit the freeboard region through the top of the fluidized bed furnace. A heat exchanger within the fluidized bed as well as the tubular walls containing the fluidized bed transfer thermal energy due to combustion to a working fluid passing through the heat exchanger and tubular panel walls.
In a typical fluidized bed furnace having a pneumatic transport feed system, discharge nozzles are located near the bottom of the fluidized bed above the bed support plate. The feed solids are supplied to the fluidized bed in pneumatic transport air and released into the bed at the discharge nozzles. The bed engulfs the in-bed heat exchanger and the bed bubbling dynamics create an additional load on the heat exchanger that is transmitted to the heat exchanger support rack.
Prior art non-working fluid cooled in-bed heat exchanger support racks often failed under these operating conditions necessitating using working fluid cooled supports. It is an object of the present invention to provide a hot (not working fluid cooled) support system for an in-bed heat exchanger that will transmit the load on the heat exchanger to the rack supports without failing.